A touch screen panel (TSP) is a panel having a sensor embedded therein, which recognizes coordinate values of touched points and detects the positions to process specific functions, when users press or touch the screen with one or more fingers, without using input devices such as a keyboard and a mouse. The touch panel, which is a main component constituting the touch screen panel (TSP), along with a controller IC, driver software (SW), and the like, is comprised of an upper plate (film) and a lower plate (film or glass). On the upper plate, a transparent electrode or a transparent conductive film (ITO) is deposited. The touch panel serves to detect a signal generating position according to a contact or a change in electrical capacity, thereby transmitting the detected position to the controller IC.
Recently, a demand for touch panel has increased with the growth of a full touch mobile phone. A demand for a touch panel for a notebook and a tablet PC that have a large area has increased.
The touch panel is classified into a resistive touch panel, a capacitive touch panel, an ultrasonic (SAW; Surface Acoustic Wave) touch panel, and an infrared (IR) touch panel, according to applied technologies. Among them, the resistive touch panel and the capacitive touch panel have been mainly used.
In the resistive touch panel, when users touch the substrates with a finger or a pen, the transparent electrodes on the upper and lower substrates disposed at a predetermined distance contact each other and thus electrical signals are generated. As a result, the positions can be detected. The resistive touch panel has advantages in terms of low cost, high accuracy, and miniaturization, and therefore has been mainly used for Personal Digital Assistants (PDAs), Portable Media Players (PMPs), navigation, handset, and the like.
On the other hand, in the capacitive touch panel, when users touch the transparent electrode on the substrate with conductor such as one or more fingers, a signal is transferred through a constant capacitive layer—which is, for example, formed by constant current flowing in a human body when touching the electrode with one or more fingers—formed on an insulating layer and the positions can be detected. The capacitive touch panel has a strong durability, a short reaction time, and excellent light transmission. The capacitive touch panel is more excellent than the resistive touch panel in terms of its multi-touch capability, and therefore has been widely used for mobile devices recently. In a case of the capacitive touch panel, tempered glass or a plastic substrate may be applied on an uppermost layer.
FIG. 1 illustrates a structure of a general touch panel module. A PET layer 10a, two transparent conductive films 20, and glass 10b are sequentially laminated on an LCD panel 50 and each layer is bonded by an optically clear adhesive 40.
A general method of forming a metal circuit wiring on a transparent conductive material is to print silver paste. However, the silver paste printing method is difficult to implement for a circuit having a thickness of 50 μm or less, and therefore a metal deposition method has been used recently. As metal, copper or silver is mainly used. Even in the case of the metal deposition method, the thickness of the deposited metal is 0.3 μm or less, which is much thinner than that in the silver printing method, and therefore copper or silver may be oxidized in the air. Therefore, in order to address the problem, a use of an alloy or coating process has been attempted.
Japanese Patent Application Laid-Open No. 2004-2929 discloses a silver alloy including silver as a main component and elements such as Ti, Zr, Pd, and the like. The silver alloy disclosed is used for a sputtering target and may be used to prepare a reflective LCD reflector or a reflective wiring electrode. However, the literature does not disclose the use of silver alloy for a touch panel. Further, the alloy does not include Nd.
Korean Patent No. 908,101 discloses a touch panel including Cu or Al as a metal coating layer and a preparing method thereof. In addition, a pad for a touch panel uses Cu, Ag, and Al for formation of a pattern and Ni/Cr, Ni/Cu, and Mo for protection from moisture and salt. However, alloys such as Cu and Ni/Cr, Ag and Mo, and the like, that have been used in prior art, are oxidized or stained by high-temperature and high-humidity environment or by the component constituting sweat such as salt so that electrical characteristics have been degrade.